Parkinsonism Drugs

Levodopa is always administered with a peripheral decarboxylase inhibitor (carbidopa or benserazide) because levodopa alone causes significant peripheral conversion. Which organ is most vulnerable to the adverse effects of peripherally formed dopamine?

A 68-year-old man from Delhi presents with a 3-year history of progressive tremor at rest, rigidity, and bradykinesia. He was started on levodopa-carbidopa 6 months ago with excellent initial response. However, over the past 2 months, he has developed unpredictable fluctuations in motor performance—periods of good mobility alternating with sudden "off" episodes where he becomes nearly immobile. His wife reports he also has involuntary writhing movements of the limbs during his "on" periods. Which of the following pharmacological mechanisms best explains the development of these motor complications?

A 62-year-old man with Parkinson's disease is started on dopaminergic therapy. Which is the most common adverse effect encountered with levodopa monotherapy in the first few weeks of treatment?

A 62-year-old man with Parkinson's disease is being counselled about dopaminergic agents. Which of the following statements about antiparkinsonian drugs is NOT true?

A 58-year-old woman with Parkinson's disease is on levodopa-carbidopa therapy and has developed motor fluctuations. Her neurologist is reviewing adjunctive agents. Which of the following drugs is NOT recommended as an adjunct to levodopa in fluctuating Parkinson's disease?